1. Field Of the Invention
The present invention relates to power-driven tools, such as wrenches and, in particularly, to arrangements for retaining socket tools on the drive anvils of such power tools.
2. Description of the Prior Art
Several different techniques are commonly used for retaining socket tools on the drive anvil of a power tool, such as a pneumatically-driven impact wrench. These techniques are illustrated in FIGS. 2-4 of the drawings. As used herein, the term "socket tool" encompasses any tool adapted to mateably engage the drive anvil, such as socket wrenches, adapters, extensions and the like. While an adapter is shown in FIGS. 2-4 for purposes of illustration, the same principles apply to other types of socket tools.
One common arrangement, illustrated in FIG. 2, includes an anvil drive lug 10 having a peripheral groove 11 formed adjacent to the distal end thereof, in which a wire ring or rubber O-ring 12 is seated. The drive lug 10 is typically square in transverse cross section, but could have other shapes. The socket tool 15 has a socket receptacle 16 therein, typically square in transverse cross section, which mateably receives the anvil drive lug 10. The ring 12 provides a friction fit to frictionally retain the socket tool 15 on the anvil lug 10. This arrangement permits the socket tool 15 to be easily mounted on and removed from the anvil lug 10. However, there are many applications which require a permanent or semi-permanent installation of the socket tool on the anvil drive lug, and the arrangement of FIG. 2 would not be suitable for such applications. Furthermore, the ring 12, which is frequently formed of an elastomeric material such as a suitable rubber, tends to wear out and must be frequently replaced. Furthermore, this arrangement will not reliably retain heavy sockets.
In FIG. 3 there is illustrated another prior art arrangement in which an anvil drive lug 20 has a cylindrical bore 21 formed transversely therethrough substantially perpendicular to opposite faces thereof. The socket tool 25 has a socket receptacle 26, and a cylindrical bore 27 formed diametrically therethrough. The anvil drive lug 20 is inserted in the socket receptacle 26 with the bores 21 and 27 in alignment for receiving therethrough a retaining pin 28, which is retained in place by means of an O-ring 29 seated in a circumferential groove 29a in the outer surface of the socket tool 25. The pin 28 can be tapped out of the bores 21 and 27 after removal of the O-ring 29 to disengage the parts.
FIG. 4 discloses another prior art arrangement in which the anvil drive lug 30 has a bore 31 formed centrally in one of the faces of the drive lug perpendicular thereto and receives therein a compression spring which outwardly biases a detent pin 33, which may be retained against expulsion by a retaining pin 34 or other well-known retaining means. The socket tool 35 has a socket receptacle 36 with a radial bore 37 in the tool 35 which communicates with the receptacle 36 and receives therein the detent 33 when the anvil drive lug 30 is inserted in the socket receptacle 36, for retaining the parts in an engaged condition. For disengagement the detent pin 33 may be depressed by inserting a suitable object in the bore 37.
Each of the arrangements of FIGS. 3 and 4 affords an effective permanent or semi-permanent coupling of the parts. However, it has been found that the bores formed in the anvil drive lugs 20 and 30 severely weaken those lugs. Indeed, impact wrench life testing has shown an 80% decrease in the life of the anvils 20 and 30 as compared with a non-bored anvil, such as the anvil drive lug 10. If a drive lug fails it must be replaced. This is a significant inconvenience, since it requires replacement of the entire anvil which, as can be seen in FIG. 1 (described below), is many times larger than the drive lug itself. Thus, the anvil itself is relatively expensive and its replacement requires disassembly of the associated power tool.